[Haskell-beginners] How to call popCnt64#?

[Michael Snoyman]

Here's an example:

{-# LANGUAGE MagicHash #-}
import GHC.Prim
import GHC.Types
import Data.Word

main :: IO ()
main = do
    let word = 5 :: Word
        res =
            case word of
                W# w -> W# (popCnt64# w)
    print res


On Sun, Mar 20, 2016 at 12:19 PM, John Ky <newhoggy at gmail.com> wrote:

> Hello Haskellers,
>
> Does anyone know how to call popCnt64# from the GHC.Prim module?
>
> This was my failed attempt:
>
> λ> popCnt64# 1
>
>
> <interactive>:14:11:
> Couldn't match kind ‘*’ with ‘#’
> When matching types
> a0 :: *
> Word# :: #
> Expected type: Integer -> Word#
> Actual type: Integer -> a0
> In the first argument of ‘popCnt64#’, namely ‘1’
> In the expression: popCnt64# 1
> In an equation for ‘it’: it = popCnt64# 1
>
> -John
>
>
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